1. Field of the Invention
This invention relates to an electric keyboard assembly which is provided with mass members each pivotally moved by depression of a corresponding key, and a method of manufacturing weight members provided in such a keyboard assembly.
2. Prior Art
Conventionally, an electronic keyboard assembly is known, in which mass members (hammer members) each having an appropriate mass are driven for pivotal movement by depression of corresponding keys, to thereby provide a simulated key-touch response of an acoustic piano.
For instance, in a keyboard assembly of this kind, seesaw-type mass members each have an arm formed with a follower, and a driving force generated by depression of a corresponding key is transmitted from the key to the follower directly or indirectly via an intermediate member, to cause pivotal movement of the mass member. Further, a proper moment of inertia is applied to each mass member e.g. by the use of a weight member mounted in the same. For instance, similarly to the case of an acoustic piano, the moment of inertia of each mass member is set such that it is progressively increased from a highest pitch key to a lowest-pitch key, for proper adjustment of dynamic key-touch response. Further, each weight member is configured for its associated key by taking a static load of the whole assembly into consideration, or an additional weight member is attached to each key, so as to reduce differences in static key-touch response between the keys to the same level as that in the acoustic piano.
Some electric keyboard assemblies of the above conventional type employ a so-called pop-up structure in which each mass member is designed to allow a free end of its arm to pop up to a position higher than the associated key. In this case, it is required to maintain space particularly above the level of the key. When weight members are provided for respective mass members, they tend to be large in size and arranged at respective free ends of the mass members to efficiently secure the moment of inertia. Further, the weight members are often mounted in a manner slightly projecting vertically from the mass members, so that they reduce space or room above and below the keyboard. Moreover, the arm on which a weight member is provided tends to be increased in length to efficiently obtain the moment of inertia. This causes an increased vertical travel distance of the weight portion of each mass member when the mass member is pivoted, which further reduces the above-mentioned space or room. For these reasons, the conventional keyboard assembly requires increased vertical space and hence tends to have an increased height (thickness).
Further, when the weight member is mounted in the vicinity of the follower which is normally formed in one arm of the mass member, the size of the weight member has to be limited to prevent interference between the weight member and keys adjacent thereto. As a result, the degree of freedom in mass distribution is limited, which hinders proper key scaling to key-touch response.
Moreover, in order to maintain excellent static and dynamic key-touch response and accomplish proper key scaling, it is often required to adjust mass distribution over each mass member and form the mass members in different configurations from each other. Mass distribution over a mass member is required to be set in consideration of not only differences between the keys ranging from the lowest-pitch key to the highest-pitch key but also differences between white keys and black keys. In other words, in spite of differences in construction, each white key and an adjacent black key are required to be substantially identical in key-touch response (reaction force). However, the white key and the black key are different in length from each other. Therefore, even if the respective positions of fulcrums of the white and black keys are set differently, when mass distribution is set for each of mass members corresponding to the respective keys in consideration of both of dynamic and static key-touch response, the mass members slightly differ in configuration from each other. As a result, the number of types of mass members used is increased, which increases the variety of configuration of the mass members, resulting in increased difficulty in mounting of mass members on the body of the keyboard assembly and increased manufacturing costs. Moreover, it is not easy to carry out mass distribution over each mass member. Therefore, in the conventional electric keyboard assembly, uniformity or consistency in construction of the mass members cannot be ensured in carrying out proper key scaling to key-touch response, especially between the low-pitch keys and the high-pitch keys or between the white keys and the black keys. In short, it is difficult to carry out key scaling to key-touch response without complicating the configurations of mass members.
Still further, when a plurality of types of weight members are attached to a mass member for adjustment of mass distribution over the mass member, the conventional electric keyboard assembly has room for improvement in respect of ease of manufacture of other types of weight members and mounting of the same and reduction of manufacturing costs.